Railway traffic controlling apparatus



May 20, 1941. E. M. ALLEN v RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Feb. 29, 1940 dwfim fi 1 2 MW flu w 9? g m mn 5 4 4 Cbc 6 Z w a 6 mm H w w 1 H S C 00 4 R 44 0 W5 r :fglmniilli--- VS d. d m. Ox a 0 V aw aw n W w w Fig].

m d d, n S w W Q. Li? M @0 9 W w P ff w m m 5 M P mm W P 0 m C M m M @W ATTORN EY Patented May 20, 1941 RAILWAY TRAFFIC CONTROLLING APPARATUS Earl M. Allen, Swissvale, Pa., assignor to The Union :Switch & Signal Company, Swissvale, Pa, a corporation of Pennsylvania Application February 29, 1949, Serial No.1 215538 8 Claims. (01. 2'46-38) My invention relates to railway trafiic controlling epparatus, and more particularly to apparatus for railway signal systems using coded energy of the time code type.

Railway signal systems using time codes each of which has acyclic pattern consisting of one on and one oif vperiod have been proposed, the relative and the absolute durations of the-code ,periods being preselected so 'as to provide a different code for each of several different conditions. Slow release relays or slow pick-up relays, or a combination of both are used as the decoding means, such relays responding to diiferent combinations according to the different durations of the code period'sof thedifferent codes.

Accordingly, a feature of :my invention is the provision of novel and improved decoding means for a signal system using coded energy of the time code type. I

A further feature of my invention is the provision of novel and improved means for :a signal system of the type here contemplated to compensa-te the effects of temperature variations on the operating time of the decoding means.

Again, a feature of my invention is the provision of novel and improved apparatus to detect coded energy of different time codes wherein a repeater code following relay differentiates between long and short code periods and standard slow acting relays can be used to decipher the specific codes.

The above feataure as well as other advantages of my invention I attain by providing a decoding transformer in which magnetic energy is made to build up and decay in step with the on and off periods of the particular codeoperating a master code following relay to induce time spaced electromotive forces in two secondary windings of the transformer. The electromotive force .induced in a selected one of such secondary windings is rectified and used to energize a slow release repeater code following relay, the slow release period of which relay is selected to bridge the short code period used but not the long code period so that this repeater relay is retained picked up for a short code period but is operated during a long code ,period. Operation of the repeater code following relay is used to cause magnetic energy to build up and decay in a second decoding transformer to create an electromotive force in a secondary winding of that transformer. This latter .electromo-tive force is applied to one or the other of two decoding relays over contacts of the master code following relay to selectively energize such decoding relays according as the repeater code fol-lowing relay is operated during a long on code period or "during a long off code period. Asymmetric units are interposed in the circuits of the decoding relays as an aid to the selection of such decoding relays.

The electro-nioti-ve force created in the second secondary winding of the first decoding transformer :is i-recti-fied and used to energize a slow release decoding relay to check the presence of co'ded energy.

This group of three decoding relays, one gov erned by the master code following relay alone and the other two governed jointly by the master and repeater code "following relays are used to selectively govern operating circuits of a signaling device and to control other signal control circuits.

To' com pensate the effects of variations in am bient temperature on the operating periods of the decoding relays, I interpose asymmetric units having negative temperature characteristics such as possessed by a copper oxide rectifier unit in the various circuits as required, and certain ones of which units serve as an aid in the selection of the decoding relays as mentioned hereinbefore. Other asymmetric uni-ts are also interposed at selected points in the decoding relay circuits to avoid the so called pumping action of the decoding relays in the event short circuit conditions *of the circuit elements occur.

'Isha-l-l-describe one formef apparatus embodying my invention and shall then point out the novel features thereof in claims.

In the accompanying drawing, Fig. l is a diagram-matic View showing apreferred form of apparatus embodying my invention when used with a four-block five-indication signal system for railways. Fig. 2 is a diagram illustrating four different time codes that may be used with the apparatus of Fig, 1.

It is to be understood, of course, that my invention is not limited to a four-block five-indication signal system for railways and this one use serves to illustrate the many places where apparatus embodying my invention is useful.

Referring to Fig. -1, the reference characters is and rib designate the track rails of a stretch of railway over which trailio normally moves in the direction indicated byan arrow. The track rails are formed by the usual insulated rail joints into consecutive track sections of which sections only the one section W-X and the adjoining ends of the two adjacent sections are shown for the sake of simplicity since these are suflicient for a full understanding of my invention. Each track section is provided with a track circuit comprising a source of coded current connected across the rails at one end of the section and a code following track or master relay connected across the rails at the other end of the section.

Any one of the several well-known means for supplying coded current may be used and as here shown the means for supplying coded current to the track circuit of section W-X includes a battery KB and a relay XR together with trafiic controlled code transmitting circuits to be later described. At this point in the description it is sufiicient to point out that when relay XR. is picked up closing front contacts 4 and 6, the battery XB is connected across the rails at the exit end of section WX to supply current thereto and when relay XR is released opening front contacts 4 and 6 and closing back contacts and 1, the battery X3 is disconnected from the rails and the rails are short circuited. Hence cyclic operation of relay XR each cycde of which consists of a preselected period during which relay XR is picked up and a preselected period during which relay XR is released, causes direct current of a time code having a cyclic pattern of one on and one on period to be supplied to the track circuit of section W-X, the duration of the on code period corresponding to the duration of the period the relay 'XR is picked up and the duration of the oii code period corresponding to the duration of the period the relay XR is released At the left-hand end of Fig. 1 there are shown a relay WR and a battery WB which are associated with the track circuit for the section next in the rear of section WX for supplying coded current to the track circuit for such section in the same manner that relay XR and battery XB supply coded current to the track circuit of section WX.

Looking at Fig. 2, four difierent time codesare illustrated that may be used with the apparatus of Fig. 1 to reflect four diiferent trafiic conditions, a fifth trafiic condition being reflected in the usual manner by the absence of coded current. In the diagrams of Fig. 2, the on periods of a code are represented by the raised portions of a curve and the on" periods of the codeare represented by the depressed portions of the curve. Under a first or approach trafiic condition, relay XR, for example, is operated in cycles during each of which it is picked up for substantially .1 second and released for substantially .1 second, and the track circuit current has a cyclic pattern consisting of an on period of .1 second and an off period of .1 second. Under a second or approach-slow traflic condition, relay XR is picked up for .9 second and released for .1 second each operation cycle and the track circuit current has a cyclic pattern consisting of an on period of .9 second and an ofi period of .1 second. Under a third or approach-medium trafiic condition, relay XR is picked up .1 second and released .9 second each operation cycle and the cyclic pattern for the track circuit current consists of an on period of .1 second and an off period of .9 second. Under a fourth or clear traffic condition, relay XR is picked up .9 second and released .9 second each operation cycle and the cyclic pattern for the track circuit current consists of an on period of .9 second and an off period of .9 second. As stated hereinbefore, a fifth or stop tramc condition is effected by the absence of coded current or by non-coded current. Relay WR is operated in a manner similar to relay XR and when so operated is effective to "7 5 impress corresponding cyclic patterns on the current of the track circuit of the section next in the rear of section W-X. The circuit means by which each of the relays XR and WR is operated in accordance with different traffic conditions to produce the time codes illustrated in Fig. 2 will appear as the specification progresses.

It is to be understood that my invention is not limited to the cyclic patterns illustrated in Fig. 2 either as to the relative or as to the absolute durations of the on and off code periods, and the relative as well as the absolute durations of the on'and off code periods can be selected as desired within the operating limits of the associated apparatus. The cyclic patterns illustrated in Fig. 2 are one selection that is satisfactory. It is to be observed that in the codes of Fig. 2, the .1 second code period represents a relatively short period and the .9 second code period represents a relatively long period.

A code following track or master relay WTR is connected across the rails adjacent the entrance end of section W-X for operation. by the coded current supplied to the track circuit of that section. Relay WTR is a direct current neutral relay of the usual type and hence is energized and picked up closing front contacts 8 and 25 when current flows in the track circuit during each on code period and is released closing back contacts 9 and 39 when no current flows during the off period of each code cycle. In other words, code following relay WTR is operated in step with the on and off periods of the cyclic pattern of the different codes impressed upon the current of the track circuit of section WX.

The durations of the on and ofi periods of the code operating the track or master code following relay WTR are determined by causing magnetic energy to build up and decay in a magnetic core I9 of a decoding transformer DTI, in step with the operation of relay W'IR, and using the electromotive forces created by such building up and decay of magnetic energy to operate a code following repeater relay TP.

When code following relay WTR is released closing back contact 9 direct current is supplied to the left-hand portion of a primary winding I I of transformer DTI from a source of direct current whose terminals are indicated at B and C, and magnetic energy is built up in magnetic core I0 of the transformer. When relay WTR is picked up to open back contact 9 and close front contact 8, the flow of current in the lefthand portion of primary winding I I is interrupted and current is supplied to the right-hand portion of primary winding II. This reversal in the direction of current in primary winding I I causes the magnetic flux of core It to die down, pass through zero and build up in the reverse direction. Such change in the magnetic flux of core III creates an alternating electromotive force in each of the secondary windings I2 and I3 of transformer DTI. When relay WTR is next released to open front contact 8 and close back contact 9 the flow of current to the right-hand portion of primary winding I I is interrupted and current is supplied to the left-hand portion of that winding. The resultant decay and building up of the magnetic flux in core I9 is substantially the same as before except the relative direction of the flux is reversed. In this latter case an 'electromotive force is induced in each of the windings I2 and I3 the same as before, except of opposite relative polarity. Hence a cycle of electromotive force is created or induced in each secondary winding l2 and 13 when relay is picked up at the beginning of each on code period and also when relay WTR :is released at the beginning of each off code period. It follows, therefore, that the electromotive forces crea'ted in secondary windings l'2 and 43 [are in each case relatively short and of a duration less than either code period and are spaced apart a time interval corresponding to the duration of the on and on code periods of the particular code operating relay W'TR.

The electromo'tive forces induced in secondary winding 13 are rectified at rectifier M and supplied to winding l5 of repeater relay 'I'P to energize that relay. Relay TP isadjusted to be effectively energized and picked up in response to each electromotive force induced in secondary winding l3. Relay TP is provided with a "slow release period slightly greater than the short .1 second code period but less than the long .9 seccnd code period. Hence when relay is operated by the approach-coded Fig. 2 and the electromotive forces induced in secondary winding [-3 are spaced apart about .1 second, the repeater relay I? is retained picked up. When-relay WTR is operated by the approach-slow code of Fig. 2, the repeater relay remains picked up for the .1 second ofi' period but "is released during each .9 second on period. Likewise when relay W'IR. is operated by the approach-medium code of Fig. '2, the repeater relay TP remains picked up during the .1 second on period but is released during each .9 second off period, and when relay WIR is operated by the clear code of 2, repeater relay 'TP is operated during each .9 second on and off code period. Furthermore when relay WTR is not operated due to "the absence of coded energy, or is retained "picked'up due to the presence of non-coded energy, repeater relay TP remains released. It is to be seen therefore that repeater code following relay 'TP differentiates between the short and long code periods.

The electromotive forces induced in secondary winding I2 of transformer D1! are rectified and applied to a decoding relay AH :OVBI' a front contact of repeater relay TP to check the presence of coded energy. To be explicit, the terminals of secondary winding l2 are connected with the input terminals of a full wave rectifier H over a frcmt contact I8 of repeater relay "T? and the output terminals of rectifier H are connected with winding l6 of relay AH. Relay AH is adjusted to be effectively energized and picked up in response to each electromotive force induced in secondary winding [2 and is provided with a slow release period slightly greater than the .9 second used for the long code period. Furthermore, the parts are so proportioned that when relay WTR is operated to create an electromotive force in each of secondary windings l2 and 13, the electromotive force created in winding 13 will cause the repeater relay "TP to be picked up closing front contact 18 :in time for -the l'ectromotive force created in winding 1 2 by the .same operation of relay WTR to effectively energize relay AH and pick up that relay. Consequently, decoding relay AH is energized and retained picked up when relay WTR is operated by :any one of the different codes of Fig. .2 providing, of course, that the repeater relay :is also picked up each code period to close front contact l8.

Long on and .long .off code periods are detected by having the operation of the. code following repeater relay TP create electromotive forces in a second decoding transformer 'DTZ and applying .suc'h electromotive forces to slow release decoding :rela'ys .BH and AD over contacts of the master :code following relay WTR. With relay AH picked up closing front contact I!) and relay operated to alternately open and close back contact 20 and front contact 21 direct current is supplied to the two portions of primary windmg 2 22 50f decoding transformer DT2 with the result an electro-motive force is induced in the secondary winding 23 of transformer DTZ each operation of :relayTP. The electromoitive force induced in secondary winding '23 of transformer 1351 2 is applied to either relay DH or AD according as the master code following relay WTR is picked up :or released. To be explicit, a circuit can be traced from the lower terminal of secondary winding 23 over an asymmetric unit 24, wire 35,.tront-contact'25of relay WTR, wire 26, asymmetric unit 21, winding 28 of relay BH and wire 29 to the upper terminal of secondary winding 23. Also a circuit can be traced from the lower terminal of secondary "winding 23 over asymmetric unit 24, wire 35, back contact 36 of relay W'I R, wire 3|, asymmetric 'unit 32, winding .33 of relay AD and wires 34 and 29 to "the upper terminal of secondary winding 23. The asymmetric units 24, 21 and 32 are disposed with their low resistance direction as indicated in Fig. 1. Hence when relay WTR is picked up closing front contact the electromotive force induced in secondary winding 23 causes current to flow in winding 28 of relay 'BH to energize that relay providing the electromotive force is of a polarity that causes the lower terminal of secondary winding 23 to be positive and the upper terminal to be negative but that an electromotive force of the opposite polarity is ineffective to energize 'relayBH. Likewise when relay WTR is releasedclosing back contact 33 and an electromotive force is induced in secondary winding 23 of the polarity that makes its lower terminal positive and "its upper terminal negative, current flows in winding 33 of relay AD to energize that relay but an electromotive force of the opposite polarity is ineifective to energize relay AD. The

manner whereby the electromotive forces induced in secondary winding 23 are of the preselected polarity effective to energize relays BH and AD will shortlyappear.

Preferably an asymmetric unit 36 is connected between wire and the upper terminal of secondary winding 23, and asymmetric units 31 and 3B are connected across relay BH and AD, respectively, as will be understood by an inspection of Fig. 1. These latter asymmetric units are disposed with their low resistance direction as indicated in the drawing and serve, as will appear hereinafter, to provide protection against the so-called pumping action of the decoding relays when short circuit conditions occur, and to also improve the operation of the apparatus.

.A slow pick-up slow release repeater relay ED is control-led over a simplecircuit including front contacts 39 and 4B of relays BE and AD, respectively.

The decoding relays AH, BH and. AD, and the repeater relay .BD control the operating circuits of a wayside signal WS which governs traffic through section W-X, and the code transmitting circuits for relay WR associated with the track circuit for the section next in the rear of {section W-'X. Repeater relay ED is provided to-avoid possible signal flashing of the wayside signal and may not be needed.

Wayside signal WS may be any standard type of wayside signal and as here shown it comprises two Searchlight signal mechanisms SI and S2. In accordance with the well-known construction for Searchlight signals, each mechanism SI and S2 includes a rotor 4| and a field winding 42 for operating three color screens G, R and Y in front of an illuminated lamp 43, the parrticu lar color screen positioned in front of the lamp being in accord with the energization of field winding 42. When field winding 42 of such signal mechanism is deenergized, the associated rotor 4| is biased to a position where the red color screen R is moved in front of the lamp and a red light is displayed. When field winding 42 is energized by current of reverse polarity, the rotor 4| is operated to move the yellow color screen Y in front of the lamp and a yellow light is displayed, and when winding 42 is energized by current of normal polarity rotor 4| is operated to move the green color screen G in front of the lamp and a green light is displayed. As indicated diagrammatically, the rotor 4| of each signal mechanism operates circuit controlling contacts in the usual manner for such searchlight signals.

A code transmitter CT is also included in the apparatus. The code transmitter is preferably of the well-known motor driven type and in this instance it is provided with three contact members 45, 46 and- 47, each of which contact members is operated in a cyclic manner as long as current is supplied to the motor element of the code transmitter. In the form of the invention disclosed in Figs. 1 and 2, code transmitter CT is arranged so that in the cyclic operation of contact member 45 it is up to engage a contact 44 for a .1 second and is down to engage a contact 48 for'.l second. In the cyclic operation of con tact member 46, it is up to engage a contact 49 for .9 second and is down to engage a contact 59 for .1 second; and in the cyclic operation of contact member 41, it is up to engage a contact 5| for .9 second and is down to engage a contact 52 for .9 second.

The code transmitterCT controls the circuits for relay WR associated with the section next in the rear of section W-X, such circuits being also controlled by the group of decoding relays associated with section W-X and by the contacts operated by the signal mechanisms SI and S2 as will shortly appear. Since relay XR is controlled in a manner similar to relay WR, it follows that relay XR is controlled by a code transmitter and other apparatus associated with thetrack circuit of the section next in advance of section W-X. 7

It is believed that the operating circuits for signal WS as well as the circuits for controlling relays WR and KR canbest be understood by a description of the operation of the apparatus. In describing the operation of the apparatus of Fig. 1 I shall first assume a train occupies section WX shunting the track circuit and causing code following track relay W'IR to be inactive with its back contacts 9 and 3!] closed. Under this traffic condition all of the decoding relays AH, BH and AD and the repeater relay BD are released because code following relay WTR is inactive and no electromotive forces are induced in the secondary windings I2 and I3 of transformer DTI. With the decoding relays all re-' leased, the operating circuit for winding 42 of each, ofthe signal mechanisms SI and S2 is open and each mechanism is biased to a position where the respective color screen R is placed in front of the lamp, and the signal WS displays a red light over a red light for a'stop signal indication. Relay WR associated with the track circult of the section next in the rear is now provided with a circuit which can be traced from terminal B of the current source over contacts.

55-46 and 51-58 of mechanism SI both closed when winding 42 of that mechanism is deenergized, wire 59, contact 4544 of code transmittor CT, wire 69, contacts 6Ifi2 and 63-64 of mechanism S2 both closedwhen winding 42 of that mechanism is deenergized, wire t5, Winding of relay WR and to terminal C of. the same source of current. Since contact 45-44 of code transmitter CT is opened .1 second and closed .1 second each operation cycle of contact member 45, the relay. WR is-released .1 second and picked up .1 second each such operation cycle so that the approach code-of Fig. 2 is impressed upon the track circuit current for the section next in the rear of section WX as long as the train occupies section W-- -X.

I shallnext assume the train in section W- advances to the right and occupies the section next in advance of section W-X. Relay XR which is controlled by the apparatus for the track circuit of the section next in advance in the same manner that relay WR is controlled by the apparatus associated with the track circuit of section W-X is now operated to impress the approach code upon the current of the track circuit of section WX and code following track relay WTR is correspondingly operated.

With master code following relay WTR operated in stepwith the short .1 second on and off periods of the approach code, the repeater relay TP is energized and retained picked up since its slow release period is sufficient to bridge the short code period. With relay TP retained picked up closing front contact I8, the electromotive forces induced-in secondary winding I2 of transformer DTI are applied to relay AH and relay AH is energized and picked up, it being recalled that the slow release period of relay AH is of the order of .9 second sufficient to bridge even the long code period; Since repeater relay TP is retained picked upno electromotive forces are induced in the secondary winding 23 of the second decoding transformer D'I2 and consequently the decoding relays BH and AD and in turn repeater relay BD are all "deenergized and released.

With relay AH picked up closing front contact 65 and relays'BH, AD and BD released, current of reverse polarity is supplied to winding 42 of mechanism SI over a circuit that includes the pole changing back contacts 61 and 68 of relay AD as will be readily understood by an inspection of Fig. 1, and mechanism SI is operated to move the yellow color screen Y before the respective lamp 43 to display a yellow light. Winding 42 of mechanism. S2 remains deenergized so that its red screen R is before the lamp, and hence signal WS now displays a yellow light over a red light to give'an approach signal'indioation. Relay WR for. the section next in the rear is now provided. with a circuit comprising terminal B, contact 55'59of. mechanism SI closed when that mechanism is operated to display a yellow light, front contact TI) of relay AH, contact 46-49 of code transmitter CT, wire 60, contacts 6I-t2 and 63-=-64 of mechanism S2, wire 65, winding of relay .WR- and terminal- C.- Since contact 46-49 is closed for .9 second and open for .1 second: each. operation cycle of contact member 46, relay'WR: is operated accordingly to impress the approachslow code of Fig. 2 on the currentiof the: track circuit for the section next in the rear to indicate that section W-X is unoccupied and the section next in advance of section W-'X is occupied I shall next assume that the train. moves to the right out of the section next in advance of section WX and occupies the second section in advance of section WX, the first section. in advance being unoccupied; Since relay X8; is controlled. in the same manner asrelay WR, relay XR is now controlled to impress the approachslow code upon the current of the track circuit for section WX and relay WTR correspondingly operated.

Assuming that the first code period to'reach relay WTR is an on period and relay W'I'R' is picked upat the beginning of this on period, the repeater relay TP and the decoding relay AH are sequentially energized and picked. upin themanner explained hereinbefore; Repeater relay T? is released during the long- .9 second on period but decoding relay AH remains picked up due to its long slow release period; With relay AH picked up closing front contact; t9 and repeater relay TP released to open front contact 24 and close back contact 2%; the reversal in the direction of current flowing through primary winding 22 of transformer DTZ induces anelectromotive force in secondary winding 23 of that trans former. The connections of the windings oftransformer DT2 are such that this electrometive' force-created in response to release of relay TP is of the preselected polarity which causes the lower terminal of winding 23 to be positive and the upper terminal to be negative and consequently current flows in the winding 28 ofrelay Bi-i' because relay WTR is picked up closing front contact 25. At the beginning ofthe next off period of the code and relay WTR is released; relay TP is again picked up and a new impulse of current is supplied to: decodingrelay AH to retain that relay" energized; Relay TPremains picked up for this short" .1 second off period. At the beginning of the next on period both relays TP' and AH are provided with a new energizing impulse of current, but relay TI? releases at the end of its slow release period during this on period of the code and in releasing causes an energizing current impulse to:b'e, supplied to the decoding relay BE in the manner explained for the first on period of this code. Consequently under this approach-slow code, decoding relays AH and EH are picked up and relays AD and BD are released. It is to be observed that the electromotive force induced in secondary winding 23 of transformer DT2 when repeater relay T? is picked up at the beginning of each off code period is of a polarity opposite to'the aforementioned preselected polarity and is ineffective to energize relay AD because of the presence of the asymmetric units 32 and 24 interposed in the circuit for relay AD although the circuit is closed at back contact 39 of master code following relay WTR during the off period of the code.

With relay AH picked up closing front contact 6t and relay AD released closing back contacts 61 and 68, the winding 42 of mechanism S! is energized at reverse polarity the same asunder the approach code. With relay BH picked up closing front contact 72 an operating circuit is formed from terminal B over front contacts 68 and 12, back contact 13 of relay BD, winding' 42 dication;

of: mechanism S2: and back contact M of relay BD' to terminal C, and winding 42 of mechanism S2 is energized at reverse polarity to move the associated color screen Y before the associated lamp so that signal WS now displays a yellow light over a yellow light for an. approach-slow signal indication. Relay WR is now provided with a circuit comprising terminal B, contact 55-59 of mechanism-1SLfrontcontact lii of relay Al-Lc'ontact 48-45%! of code transmitter GT, front contact 15 0f relay EH, contact M of mechanism S2 closed when that mechanism displays a yellow light, wire 65 winding ofrelay- WR and terminal C. Since contact :lE- liil of code transmitter CT- is closed .1 second and open .9 secondeach operation cycle of contact member 4-5 the relay WR is operated to impress the appreach-medium" code of Fig. 2 upon the current of the" associated track circuit to indicate that two sections next in advance of the associated section are unoccupied and the third section in advance'is occupied.

Assuming next that the train advances to the right another track section so that there are two unoccupied sections between section W X and the section occupied thetrain, the relay XR; is operated to impress the" approach-medium code on the track circuit current of section W'X. Assuming the first code period to reach relay WTR of this approach-medium code is an on period and theu'elay-ispicked up; the repeater relayTP- and" decoding relay AH are sequentially ener-- ized and" picked up as previously explained. Re-' peater relay T]? and relay AH are. both held picked up during this .1' second on period and each of these relays is supplied with a new energ'izing impulse of" current when relay WTR' is released at the beginning of the'next off period of the code. Repeater relay TI? releases however during the .9 second oif'period and when it releases to operate contacts 2i and 20 an electromot'ive force is induced in secondary winding 23 of transformer DTZ' which electromotive force is of "the aforementioned preselected polarity and current flows in" the winding 33 of relay AD because the' circuit. to relay AD is now closed at back contact 3'9 of the code following relay WTR.

Hence decoding relay AD is energized and picked up. When repeater relay TP is picked up at the beginning of the next on code period. the elect'rornot'ive force induced in secondary winding 23 is opposite in' polarity to that of the preselected polarity'and hence is inefiective to energize relay BH because of the presence of the asymmetric units 24 and 2.! although front contact 25 of relay WIR is now closed to complete the circuit for relay BH; Decoding. relay BH is therefore deenergiiz'ed' and released at the end of its slow release period. Itlfollows that under the approachmedium code decoding relays AH and AD are energized and picked up; but relays-EH and ED arer'eleased.

With this set-up of the decoding relays. the operating. circuit for winding 42 of mechanism SI isv pole changed at'front contacts 1'! and 18 of relay'AD and mechanism Si is energized at normal polarity'to operate color screen G in front of the associated lamp. The operating circuit for winding 42 of mechanism S2 is completed the same as under the approach-slow code except the=circuitincludesfront contact 79 of relay AD in place of front contact 12 0f relay Bil. Thus signal WS now displays a green light over a yellow" light for an approach-medium signal in- Relay WR isnow provided with a circontact 64-76 of mechanism S2, wire 65 and winding of relay WR to terminal-C. Since contact 4152 of code transmitter CT is closed .9 second and open .9 second each operation cycle of contact member 47, relay WR is operated to impress the clear code of Fig. 2 upon the current of the associated track circuit in response to the three sections next in advance of the associated track section being unoccupied.

Assuming the train moves another section to the right so that there are three unoccupied sections between the section occupied by the train and section WX, relay XR which is operated similar to relay WR isnow operated to impress the clear code upon the current of the track circuit of section W,X and the code followin master relay W'IR is correspondingly operated.

Assuming that the first code period to reach code following relay WTR is an on period, the repeater relay TP and decoding relay AH are accordingly energized and picked up as in the previous cases. Repeater relay TP however is released at the end of its slow release period during the long .9 second on period and in so doing causes an electromotive force to be induced in secondary winding 23 of transformer DTZ which is of the preselected polarity and current is supplied to decoding relay BH to pick up that relay because front contact 25 of relay WTR is now closed. At the start of the off period and relays TP and AH are supplied with an energizing impulse of current the repeater relay TP is again picked up and relay AH is retained picked up. The electromotive force induced in secondary winding 23 because of the picking up of repeater relay TP is opposite in polarity to the preselected polarity and is ineifective to energize relay AD. However repeater relay TP is released at the end of its slow release period during the long .9 second off period and this release of relay TP causes an electromotive force to be induced in secondary winding 23 which is of the preselected polarity and which is applied to decoding relay AD to energize that relay. It is to be seen therefore that under the clear code decoding relays AH, BH and AD are all energized and picked up.

' gized at normal polarity the same as under the approach-medium code. The circuit for winding 42 of mechanism S2 is pole changed at front contacts 82 and 83 of relay BD so that mechanism S2 is now energized at normal polarity and operated to move its green color screen G in front of the associated lamp with the result that signal WS displays a green light over a green light for a clear signal indication. Relay WR is now provided with a circuit comprising terminal B, contacts 55-56 and 5l--86 of mechanism SI, contact 47-5! of code transmitter CT, front contact 84 of relay BD, contacts 6l-85 and 63-64 of mechanism S2, wire 65 and winding of relay WR to terminal C. Consequently relay W'R is still operated to impress the clear code upon the current of the associated track circuit since contact 41--5l is closed for .9 second and open for .9 second each operation cycle of code contact 41.

The asymmetric units 24, 21 and32 are pref-; erably of the type characterized by a decrease :in

' perature.

resistance in the forward or low resistance direction when the temperature increases. Such characteristics are found in the copper oxide rectifier unit. Units 24, 21 and 32 will therefore automatically compensate for the increase in the resistance of copper windings of the associated decoding relays BH and AD in response to an increase in temperature. Furthermore these asymmetric units will automatically compensate for the increase in the resistance in the winding 23 of decoding transformer DT2 due to its increase in temperature so that the total resistance of the circuit for each of the decoding relays remains substantially uniform for all ambient temperatures. In like fashion rectifiers l1 and M are preferably of'the copper oxide rectifier type and automatically compensate for the increase in the resistance of the windings of the associated relays TP and AH and the windings of the decoding transformer DTI due to changes in ambient tem- Consequently the operating time of the several relays remains substantially uniform for all ambient temperatures.

In the event the asymmetric unit 24 should become short circuited, that is, the unit breaks down and conducts current in both directions,

' rent in both directions. Likewise the asymmetric unit 37 forms a shunt path which shunts the electromotive force of a polarity opposite to the preselected polarity away from relay BH in the event the asymmetric unit 21 should become short circuited and conduct current in both di rections. If asymmetric unit 32 associated with relay AD should become short circuited, the unit 38 serves to shunt away from relay AD the electromotive force induced in secondary winding 23 when relay TP is picked up.

Although I have herein shown and described only one form of railway trafiic controlling apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In signaling apparatus for use with a code following master relay operated by coded energy of any one of a plurality of different time codes each of which has a cyclic pattern of one on and one off period and which cyclic pattern is made distinctive by a preselected combination of predetermined short and longcode periods, the combination comprising, a code following repeater relay provided with a slow release period greater than said short code period and less than said long code period, a first circuit means including a contact of said master relay to supply an energizing current impulse of relatively short duration to said repeater relay each code period of the particular code operating said master relay to distinguish between the short and long code periods by the repeater relay being retained'picked up for each short code 'period andreleased during'each long code period, a'first and-a second decoding relay, a second cizu,

cuit means including. a contact of said. repeater relay operative when the relay isreleased: to create an energizing current impulse, another circuit means coupledto said second circuit means and including a front and: a back contact of said master relay to selectively supply said last mentioned energizing current impulse to said docoding relays according as said repeater relay is released during an onor an off code period, and signaling circuits selectively controlled by said decoding relays.

2. In signaling apparatus for use with a code following master relay operated by coded energyof any one of a plurality of different time codes each of which has acyclic pattern of one on and one off period and which cyclic pattern is made distinctive by a preselected combination of predetermined short and long' code periods, the combinationcomprising, a code following repeater relay provided with a slow acting period greater than said short code period and less than said long code period; a first circuit means including a contact of said master relayto supply an energizing current impulse of a duration less than either of said code periods to said repeater relay each code period of the particular code opera-ting said master relay to distinguish between short and long code periods by the repater relay remaining stationary for each short code period and being operated for each long code period, a first and a second decoding relay, a second circuit means including a contact of said repeater relay and atransformer to create an energizing current impulse eachtime said repeater relay is operated, another circuit means coupled to said transformer and including two contacts of said master relay one closed: during the on period and the other closed during the off period to selectively energize said decoding relays by said last mentioned energizing current,- impulse according as said repeater relay is operated during an on or an off code period; and signaling circuits selectively controlled by said decoding, relays.

3. In signaling apparatus for use with a code following master relay operated by-coded energy of any one of a plurality of different time codes each'of which has a cyclic pattern of one on and one offperiod and which cyclic pattern is made distinctive by a preselected combination of predetermined short and long code periods, the combination comprising, a code following repeaterrelay provided with a slow release period greaterthan said short code period and less than said long code period, aifirst circuit meansineluding a contact of said master relay, a transformer and" a direct current source to supply an energizing current impulse of relatively short duration to said repeater relay each code period of the particular code operating said master re-.

lay to distinguish between the short and long code periods by the repeater relay being retained pickecl v up for each short code period and released. during each long code period, a decoding relay, a second, circuit means including a back,

relay contact is closed, and a signaling circuit including aifront contact of said decoding relay.

4. In signaling. apparatus, for use with a code following master relay operated to a first and, a second position in step with the on and off periods of any one of a plurality of different time codes each of which is made up. of a distinctive combination of predetermined short and long. code periods, the combination comprising, a code following repeater relay provided; with a slow release period greater: than said short code periodv and less than said long code period, a first circuitl means including a first position contact and a second position contact of said master relay as well: as. a transformer and a direct current source to supply a relatively short single energizing currentiimpulseto said repeater relay each code periodv of the particular code operating said master relay to distinguish between the short long periods of the code. by the repeater relay remaining picked up. for each short code peri'od: and being released during each long code period, a first and a. second, decoding relay, a, second circuit means: including a contact of said repeater relay and. another transformer and a direct cu'rrentsource. to create a short energizing curent; impulse each time said repeater relay is released,v another circuit means connected to said other transformer and including either a. first I position contact or a second position contact of said master, relay to supply said last; mentioned energizing current impulse to either said first or said second. decoding relay according as said repeater relay is released. during an on or an off code.v period,. and signaling circuits selectively controlled over contacts. of said decoding relays.

54,111 signaling apparatus for use with a code following master relay operated to a first and a second. position in step with the on and ofi periods of any onev of a plurality of diiferent:

time codes each of whichis made up of a distinctiile combination of predetermined short and long code periods, the combination comprising, a first transformer, a. first circuit means including a first, and asecond position contact of said master relay to supply direct current to a primary winding; of said. transformer to induce in a secondary winding of the transformer relatively short electromoti'tre forces time spacedaccording to. the durationsof the code periods of the particular code operating said master relay, a code following repeater relay connected with said secondary Winding effectively energized by each such electromotive force, said repeater relay provided: with a slow release period greater than said short code period and less than said long code: period to retain: the repeater relay picked upzfor short code periods and to release the relay during long codeperiods, a second transformer, a, second circuit means including a contact of said repeater relay tosupply direct current to a primary winding of said second transformer to induce in a secondary winding of said second transformer an electromotive force of a preselected polarity when the repeater relay is remetric unit to connect said second decoding re lay to said secondary winding of the second transformer and disposed to pass only electromotive force of said preselected polarity to pick up the second decoding relay in response only to long or: code periods, and signaling circuits selectively controlled over contacts of said decoding relays.

6. In signaling apparatus for use with a code following master relay operated by coded energy of any one of a plurality of different time codes each of which has a cyclic pattern of one on and one off period and which cyclic pattern is made distinctive of a preselected combination of predetermined short and long code periods, the combination comprising, a first transformer, a first circuit means including a contact of said master relay to supply direct current to a primary winding of said transformer to create a relatively short electromotive force in a secondary winding of that transformer each code period of the particular code operating said master relay, a code following repeater relay connected with said secondary winding for energization of said repeater relay in response to said electromotive force,

said repeater relay provided with a slow release period greater than said short code period and less than said long code period to distinguish between the short and long code periods by the repeater relay being retained picked up for each short code. period and released during each long code period, a second transformer, a second circuit means including a contact of said repeater relay to supply direct current to a primary winding of said second transformer to create an electromotive force in a secondary winding of said second transformer in response to release of said repeater relay, a first and a second decoding relay, a third circuit means including contacts of said master relay to selectively connect said decoding relays to said secondary winding of the second transformer to selectively energize the decoding relays according as said repeater relay is released during an on or an oif code period, and signaling circuits selectively controlled by said decoding relays. 7. In signaling apparatus for use with a code followingmaster relay operated by coded energy of any one of a plurality of different time codes each of which has a cyclic pattern of one on and one off period and which cyclic pattern is made distinctive by a preselected combination of predetermined short and long code periods, the combination comprising, a first transformer, a first circuit means including a contact of said master relay to supply direct current to a primary winding of said transformer to create a relatively short electromotive force in each of a first and a second secondary winding of that transformer each code period of the particular code operating said'maste'r relay, a code following repeater relay connected with said first secondary winding effectively energized by each electromotive force created in that winding, said repeater relay provided with a slow release period greater than said short code period and less than said long code period to retain said repeater picked up for short code periods and to release the relay during long code periods, a first decoding relay connected with said second secondary winding effectively energized by each electromotive force created in that Winding, a second transformer, a second circuit means including a front contact of said first decoding relay and a contact of said repeater relay to supply direct current to a primary winding of said second transformer to create an electromotive force in a secondary winding of said second transformer each time said repeater relay is released, a second and a third decoding relay, a third circuit means including a front and back contact of said master relay to selectively connect said secondary winding of said second transformer to said second and third decoding relays to energize said second and third decoding relays according as said repeater relay is released during an on or an ofi code period; and signaling circuits selectively controlled by said first, second and third decoding relays.

8, In combination, a section of railway track; traflic controlled means operative to supply to the rails of said section current having a time code of short on and short off periods, or having long on and short off periods, or having short on and long off periods, or having long on and long oif periods according to a first, or a second, or a third, or a fourth traflic condition in ad- Vance of the section; a code following master relay connected with the rails of the section for operation thereof in step with the on and off periods of the coded current supplied to the rails, a first transformer, a first circuit means including a contact of said master relay to supply direct current to a primary winding of said transformer to create an electromotive force in each of a first and a second secondary winding of said transformer each code period, a code following repeater relay connected with said first secondary winding eifectively energized by each electromotive force created in that winding, said repeater relay provided with a slow release period greater than said short code period and less than said long code period to retain said repeater relay picked up for a short code period and to release the relay during a long code period, a first slow release decoding relay connected with said second secondary winding effectively energized by each electromotive force created in that winding, a second transformer, a second circuit means including a contact of said repeater relay to supply current to a primary winding of said second transformer to create an electromotive force in a a secondary winding of the second transformer when said repeater relay is released, a second and third slow release decoding relay connected with said secondary winding of the second transformer over a front and a back contact of said master relay respectively to energize said 

